For the preparation of hexamethylcyclotrisilazane, it is known to react dimethyldichlorosilane with ammonia according to the following reaction scheme (see J. Am. Chem. Soc., 70, 3888-91, 1948). ##STR1##
This method involves reacting dimethyldichlorosilane with ammonia in benzene at 30.degree. C., removing ammonia chloride by-product by filtration through a glass filter or the like, and distilling the reaction product to isolate hexamethylcyclotrisilazane.
Undesirably, this method can produce hexamethylcyclotrisilazane in a very low yield of about 36%. In addition, it is difficult to effectively remove the ammonium chloride by-product by filtration and even the subsequent distillation cannot remove it satisfactorily. The thus obtained product contains a relatively large amount of chloride and other impurities. That is, the final product has low purity. For this purity problem, the hexamethylcyclotrisilazane obtained by the conventional method is not regarded suitable as photoresist processing agents and other electronics materials which currently continue a remarkable advance.